Condensation in Super Shelter with VB or space blanket?

**BillyBob58** · 08-16-2009, 08:48

Originally Posted by Dutch

Could a piece of sil be used as a vb instead of the space blanket? I know you won't get the radient heat but you should still get the vb and improved dead air space. I just don't like those space blankets.

Sure. But the SBs should still serve as the VB, as long as they are reasonably water proof. I probably won't go back to the WM SB after having used the HeatSheet, which is so much nicer. But, the Wallyworld SB still always got the job done for me.

**BillyBob58** · 08-16-2009, 08:54

Originally Posted by Bumper

I'm having the same problem: my bag and everything in the hammock seemed dry but the ocf and undercover below the SB were VERY wet in the morning - to the point where the water was pooling.

This was only my second hang but I had the same problem on my first, although I didn't use the SB that time and it was very, very humid. Because of that first experience I made sure I used the SB this time but I did find it kinda hard to position correctly.

I'm wondering if this is a condensation problem due to a warm body (there must still be some heat lost through the SB) contacting the cold night air (temp= high 30's this time). If that is the case, I would expect the water on top of the ocf, not under it? I'm assuming there must be more to it than this or the people using underquilts would have the same problem.

FYI, I'm usually a very warm sleeper who sweats a lot. This particular night I felt quite cool though.

Help?

OK, this really bugs me since I have never had the problem, and I would like to know the true cause. Can it come down to difs between folks? I don't really think so, but?

Is your SB waterproof? IOW, a true vapor barrier as well as a radiant heat block?

I'm going to try and pay more attention to this in the coming winter.

In the mean time, keep the theories coming.

RRev, have you had any condensation problems on your uses last winter?

I still hope to hear from KWPAPKE. He should have had a lot of condensation.

**MacEntyre** · 08-16-2009, 08:57

If you use sil as a vapor barrier, it might do better if it is the outer layer of your insulation, outside everything.

Ed Speer and Youngblood have been experimenting with a very thin plastic sheet as an outer vapor barrier, with a SB inside. I have not seen any report from those experiments.

P.S. I bet Kurt has no condensation.

**Ramblinrev** · 08-16-2009, 11:24

Originally Posted by BillyBob58

RRev, have you had any condensation problems on your uses last winter?

I can honestly say I haven't got a clue. I guess I either didn't check or didn't care. Not sure what to tell you other than maybe I'll remember to check these things this coming cold season.

**BillyBob58** · 08-16-2009, 14:34

Originally Posted by Ramblinrev

I can honestly say I haven't got a clue. I guess I either didn't check or didn't care. Not sure what to tell you other than maybe I'll remember to check these things this coming cold season.

I think you would have noticed anything sig. Therefore, I think you had very little or none. I can tell you that one of the few times I did not use a SB and got condensation, it was very noticeable as soon as I went to exit. The foot of my pad was soaked, and the rest of it quite damp, and moisture in the UC. I'm not positive, but I think the foot of my bag was damp also. But most of the action seemed to be at the foot end of the pad. This was camped beside a river in the super damp Olympics in WA at about 48-50*F. I was still plenty warm though. And I had no more condensation the rest of the trip, using an SB.

**Ramblinrev** · 08-16-2009, 14:42

Originally Posted by BillyBob58

I think the foot of my bag was damp also. But most of the action seemed to be at the foot end of the pad. This was camped beside a river

All the more reason to hang the foot higher ...

**BillyBob58** · 08-16-2009, 14:54

Originally Posted by MacEntyre

If you use sil as a vapor barrier, it might do better if it is the outer layer of your insulation, outside everything.

Ed Speer and Youngblood have been experimenting with a very thin plastic sheet as an outer vapor barrier, with a SB inside. I have not seen any report from those experiments.

P.S. I bet Kurt has no condensation.

Right. Didn't he use a VB(space blanket or whatever) as the first layer under the hammock, then the Pea Pod plus whatever else under the SB, then another VB outside the PeaPod as a WP shell/cover? At the winter hang in VA at 11*F?

I think you could use sil or a SB right under the hammock and it would be the same as far as condensation went. But he needed the inside SB/VB to prevent condensation of body moisture being trapped by the WP outer wrap.

I have also used the SB inside the PeaPod without a hint of a problem at 11*-30F+. But if any of MacEntyre's theories of cold air entering the UC and causing condensation turn out to be correct, then the pod is a somewhat different creature. Because unless WIDE open, it "seals" across the full length of both sides of the hammock's upper edges. So there is not going to be much cold air able to sink down in there. Though I was not thinking in terms of condensation, I always theorized this was a MAJOR and mostly unknown benefit to a pod approach. And an explanation as to why a Pea Pod always seems to work so good( ever heard of anyone being cold in one at the rated temps?

) . Being "sealed" ( sort of) on both ends and along the sides, cold air just really can't get in there after you are in and Velcroed up. So gaps under you don't seem near as cold. I imagine this also precludes condensation unless caused directly by too much perspiration. Heck, I never even had any noticeable condensation with the thing completely closed!( To my complete surprise- sure was toasty though!)

**BillyBob58** · 08-16-2009, 14:57

Originally Posted by Ramblinrev

All the more reason to hang the foot higher ...

Good point! Then the moisture could have been closer to my middle via running down hill, and more fairly distributed!

**Wentworth** · 08-16-2009, 18:23

Originally Posted by BillyBob58

Heck, I never even had any noticeable condensation with the thing completely closed!( To my complete surprise- sure was toasty though!)

Nor I. By leaving an inch gape above my face, it traps so much heat I don't even need a top quilt. Haven't noticed any extra weight from moisture when packing up either. It may be heavier, but the peapod works.

**Knotty** · 08-16-2009, 20:38

Below are generalizations:

Condensation occurs when air comes in contact with a surface that is at or below the dewpoint. The dewpoint is always below the ambient temp. The reason is air can hold more total water at warmer temperatures. 70 degree air at 40% relative humidity has more water in it than 50 deg air also at 40% rh. That's why they call it "relative" humidity.

Cold air from the outside entering into the SS should not condense since all the parts of the SS are either at or above the ambient temp. Now the air in your sleeping bag is warm and can hold more water, which your body provides. As this air migrates through and out of the bag it reaches colder temps and may condense. The reason you put a vapor barrier close to the heat source is because you hope it will not get cold enough to cause condensation and at the same time prevent the damp air from traveling any further. If you put the vapor barrier after the insulation the humid air from the body will reach this cold impermeable wall and condense.

My guess is the SS gets condensation inside because a space blanket on top of the open cell foam insulation is not going to stop all the moisture your body produces. The moisture which gets around the SB gets trapped by the waterproof SS undercover and condenses on cold surfaces.

IMHO the SS would work better if it was made from breathable material, though it might get wet on occasion from heavy fog.